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Influence of copper on expression of nirS, norB and nosZ and the transcription and activity of NIR, NOR and N2 OR in the denitrifying soil bacteria Pseudomonas stutzeri.

Black A, Hsu PC, Hamonts KE, Clough TJ, Condron LM - Microb Biotechnol (2016)

Bottom Line: Results revealed that 0.05 mM Cu caused maximum conversion of N(2)O to N(2) via bacterial reduction of N(2)O.As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l(-l) soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 μg g(-1) to maximize the proportion of N(2)O reduced to N(2).Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N(2)O emissions.

View Article: PubMed Central - PubMed

Affiliation: Bio Protection Research Centre, Lincoln University, PO Box 85084, Lincoln, Christchurch, 7647, New Zealand.

No MeSH data available.


Related in: MedlinePlus

Growth curve of Pseudomonas stutzeri over the course of 7 days (A). Mean N2O:(N2+N2O) ratio of each copper treatment 0, 0.02, 0.05, 0.15, 0.5, 1, 5 and 20 mM over 10‐day period (B). Standard error of the mean (SEM) are represented as error bars.
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mbt212352-fig-0002: Growth curve of Pseudomonas stutzeri over the course of 7 days (A). Mean N2O:(N2+N2O) ratio of each copper treatment 0, 0.02, 0.05, 0.15, 0.5, 1, 5 and 20 mM over 10‐day period (B). Standard error of the mean (SEM) are represented as error bars.

Mentions: Growth of P. stutzeri from anaerobic cultures over 7‐day period showed no significant difference throughout all Cu concentration, except 5.00 and 20.00 mM of Cu (Fig. 1A), and the growth reached stationery phase at day 3 with ≤ 1.00 mM of Cu. Colony counts of P. stutzeri cultures containing 5.00 mM Cu were significantly reduced compared with those in Cu concentrations < 5.00 mM with a delay in growth after day 3 (Fig. 1A). This could indicate the onset of toxicological effects, although denitrification was occurring at relatively high rate (Fig. 2B). As expected, given P. stutzeri the highest concentration of Cu (20.00 mM) inhibited the growth completely (result not shown). Daily measurements revealed production of N2O and subsequent reduction to N2 varied significantly with changes in Cu concentrations (Fig. 2B). Interestingly, the Cu‐deficient broth (control, 0.00 mM) did not produce the highest concentrations of N2O compared with the Cu‐containing treatments as has been suggested in a previous study to be the most likely outcome (Granger and Ward, 2003). Furthermore, a comparison between the total amount of N2 produced per Cu treatment revealed no significant differences. In fact, the highest amount of N2O produced was observed in the culture containing 0.15 mM, which corresponded to the amount of NO3− consumed (Fig. 3A and B). The proportion of N2O to N2O + N2 in the headspace differed significantly (P < 0.001) between Cu treatments, with the lowest proportion of N2O to total N measured in the treatments containing 0.02 and 0.05 mM of Cu (Fig. 3C). Over the 10‐day sampling period (apart from 0.50 mM Cu treatment), treatments ≥ 0.15 mM Cu resulted in a significantly higher (P < 0.001) total yield of N2O than N2. Studies that have investigated the effect of Cu addition on the conversion rate of N2O to N2 concluded that the absence of Cu resulted in an accumulation of N2O (Granger and Ward, 2003; Manconi et al., 2006; Felgate et al., 2012). However in these studies, the Cu concentration at which N2OR maintained an optimum activity and where the lowest proportion of N2O to N2 levels were generated, were not evaluated in further detail. Additionally, the presence of sulfide, especially H2S in a Cu‐deficient environment has been known to affect the reduction of N2O to N2 (Manconi et al., 2006; Pan et al., 2013). Given that in our study, S2− and H2S could have been generated during anaerobic incubation of the broth from CuSO4 (source of the Cu) and cysteine, this may have also contributed to the accumulation of N2O.


Influence of copper on expression of nirS, norB and nosZ and the transcription and activity of NIR, NOR and N2 OR in the denitrifying soil bacteria Pseudomonas stutzeri.

Black A, Hsu PC, Hamonts KE, Clough TJ, Condron LM - Microb Biotechnol (2016)

Growth curve of Pseudomonas stutzeri over the course of 7 days (A). Mean N2O:(N2+N2O) ratio of each copper treatment 0, 0.02, 0.05, 0.15, 0.5, 1, 5 and 20 mM over 10‐day period (B). Standard error of the mean (SEM) are represented as error bars.
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mbt212352-fig-0002: Growth curve of Pseudomonas stutzeri over the course of 7 days (A). Mean N2O:(N2+N2O) ratio of each copper treatment 0, 0.02, 0.05, 0.15, 0.5, 1, 5 and 20 mM over 10‐day period (B). Standard error of the mean (SEM) are represented as error bars.
Mentions: Growth of P. stutzeri from anaerobic cultures over 7‐day period showed no significant difference throughout all Cu concentration, except 5.00 and 20.00 mM of Cu (Fig. 1A), and the growth reached stationery phase at day 3 with ≤ 1.00 mM of Cu. Colony counts of P. stutzeri cultures containing 5.00 mM Cu were significantly reduced compared with those in Cu concentrations < 5.00 mM with a delay in growth after day 3 (Fig. 1A). This could indicate the onset of toxicological effects, although denitrification was occurring at relatively high rate (Fig. 2B). As expected, given P. stutzeri the highest concentration of Cu (20.00 mM) inhibited the growth completely (result not shown). Daily measurements revealed production of N2O and subsequent reduction to N2 varied significantly with changes in Cu concentrations (Fig. 2B). Interestingly, the Cu‐deficient broth (control, 0.00 mM) did not produce the highest concentrations of N2O compared with the Cu‐containing treatments as has been suggested in a previous study to be the most likely outcome (Granger and Ward, 2003). Furthermore, a comparison between the total amount of N2 produced per Cu treatment revealed no significant differences. In fact, the highest amount of N2O produced was observed in the culture containing 0.15 mM, which corresponded to the amount of NO3− consumed (Fig. 3A and B). The proportion of N2O to N2O + N2 in the headspace differed significantly (P < 0.001) between Cu treatments, with the lowest proportion of N2O to total N measured in the treatments containing 0.02 and 0.05 mM of Cu (Fig. 3C). Over the 10‐day sampling period (apart from 0.50 mM Cu treatment), treatments ≥ 0.15 mM Cu resulted in a significantly higher (P < 0.001) total yield of N2O than N2. Studies that have investigated the effect of Cu addition on the conversion rate of N2O to N2 concluded that the absence of Cu resulted in an accumulation of N2O (Granger and Ward, 2003; Manconi et al., 2006; Felgate et al., 2012). However in these studies, the Cu concentration at which N2OR maintained an optimum activity and where the lowest proportion of N2O to N2 levels were generated, were not evaluated in further detail. Additionally, the presence of sulfide, especially H2S in a Cu‐deficient environment has been known to affect the reduction of N2O to N2 (Manconi et al., 2006; Pan et al., 2013). Given that in our study, S2− and H2S could have been generated during anaerobic incubation of the broth from CuSO4 (source of the Cu) and cysteine, this may have also contributed to the accumulation of N2O.

Bottom Line: Results revealed that 0.05 mM Cu caused maximum conversion of N(2)O to N(2) via bacterial reduction of N(2)O.As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l(-l) soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 μg g(-1) to maximize the proportion of N(2)O reduced to N(2).Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N(2)O emissions.

View Article: PubMed Central - PubMed

Affiliation: Bio Protection Research Centre, Lincoln University, PO Box 85084, Lincoln, Christchurch, 7647, New Zealand.

No MeSH data available.


Related in: MedlinePlus